Impacts of roads on individual wildlife genetics

by Karl Jarvis

Roads do a fantastic job of connecting people, but they are also incredibly dangerous barriers to wildlife. Two major consequence of roads for wildlife are 1) fragmentation, and 2) roadkill. Fragmentation is a huge issue because roads divide up habitat, preventing wildlife from moving to areas where they can access food, shelter, and mates. Very few wild areas are left in the world that do not have roads or other barriers in them.  In addition, collisions with vehicles cause large numbers of animal deaths. At least one million large mammals are killed each year on US roads, and this number is dramatically higher for smaller animals.

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Kangaroo rat trapped during the night, one of many sampled for this study. Credit: K. Jarvis

Genetics are a powerful tool for understanding the impacts of roads on wildlife. Geneticists use DNA analyses to understand the impacts of fragmentation, and as a result, we know that roads cause populations of many species to be genetically divided. Animals on different sides of roads can become genetically distinct in a matter of only a few generations. However, until now, genetics has not been used to understand how roadkill impacts populations. We are currently using genetics to understand how roadkill and fragmentation differ in their effects on the genetics of wildlife.

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Kangaroo rat hops away after being sampled. Credit: K. Jarvis

Our main goal is to understand how roadkill and road avoidance affect wildlife populations. Our main study animals are kangaroo rats in the Sonoran desert of southern Arizona, whose populations are divided by roads. These kangaroo rat populations are fragmented by roads and are also prone to being killed on roads, so we hope to understand how these two factors affect their genetic patterns. To get genetic samples from the kangaroo rats, we capture them in live traps and take tiny snips from their ear tips. We get genetic information from these tissue samples to understand levels of genetic diversity across the populations. We are also using computer simulations to model how different levels of roadkill and avoidance would affect genetic patterns. By comparing simulations and actual genetics, we can understand what patterns result from highways cutting through wild lands.

This study, together with analyses of other wildlife species, such as the black bear, American pronghorn and the alpine newt will provide an understanding of how roads with different characteristics affect different species. The computer modeling approach will allow us to develop predictions of the effects of roads on wildlife and improve our ability to anticipate road effects. The results will allow us to understand how we can best reduce the impacts of roads on wildlife.